If you have access to the email you used for it, I believe you can recover it through that.
However, if you don't, try and find some sort of documentation or proof of purchase of the account, and send an email to Mojang's help desk to explain the situation and provide proof of purchase.
I've just sent that now actually, it kinda sucks though cause that account is 2011, so coming up to 7 years old etc, so if i have proof it will of probably been lost/gone regardless
